The atmospheric aerosol consists of a complex mixture of organic and inorganic compounds. The aerosol has important effects on human health, visibility, climate, and precipitation chemistry. Past effort has concentrated on the determination of number, size and bulk chemical analysis of these particles. Individual particles vary in properties such as toxicity, light attenuation and hygroscopic behavior which are functions of their shape and three dimensional chemical composition. Our group is involved in a continuing effort to characterize individual particle images and compositions using both SEM and ToF-SIMS. This combination provides information on both bulk and surface chemistry and images of single aerosol particles. This study included size segregated samples (via Al substrates in an 8 stage cascade impactor) and bulk aerosol filter samples (via 47 mm Millipore PTFE filters) from the summer 2000 Montana forest fires, from Hawaiian sea salt, and from an Asian Dust event reaching Salt Lake City, Utah in April 2001. Multivariate statistical analysis was used to extract information from the SIMS images. Images of the particles were separated from the image background, which significantly improved our ability to acquire the composition of individual aerosol particles. Montana forest fire aerosol was predominantly submicron, well within the respirable range (PM2.5), and had a characteristic surface identified as the amides of stearic acid and palmitic acid. Sea salt showed a layered structure of organic compounds on the surface of aqueous NaCl. The Asian Dust event could be clearly distinguished from normal Salt Lake City particulate pollution.